Free weight loss calculator: enter weight, goal & timeline to get TDEE, daily calorie deficit & safe target intake. Free plan, no signup.
Disclaimer: This planner is for informational purposes only and is not medical advice. It uses the standard energy-balance model (1 lb ≈ 3,500 kcal). For aggressive targets, medical conditions, or intakes near the safety floor, consult a qualified health professional before starting.
One pound of body fat stores roughly 3,500 kcal — so losing it comes down to sustained energy balance. Our free weight loss calculator turns your goal into a concrete daily plan: enter your current and goal weight, timeline, age, height, sex, and activity level, and it computes your TDEE, the daily calorie deficit required, your target intake, and projected weekly loss — with a safety-floor warning if your target drops too low.
Weight change follows energy balance: eat more than you burn and you gain; eat less and you lose. Your BMR (basal metabolic rate) is the energy you burn at rest; multiply it by an activity factor and you get TDEE (total daily energy expenditure) — your full daily burn. The calorie deficit (TDEE minus intake) is what shrinks fat stores.
The classic rule of thumb — 1 lb of fat ≈ 3,500 kcal (1 kg ≈ 7,700 kcal) — converts a weight goal into a daily deficit. A 500 kcal/day deficit predicts roughly 1 lb per week, though real loss slows over time as the body adapts, so treat projections as a starting framework rather than a promise.
Safety matters more than speed. Intakes below 1,200 kcal/day for women or 1,500 kcal/day for men are widely considered minimums without medical supervision, and losses faster than ~1 kg/week are hard to sustain and can cost muscle. This calculator flags both situations.
BMR — Mifflin-St Jeor:
Men: 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Women: 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
TDEE = BMR × activity factor (1.2 sedentary → 1.9 very active)
Total deficit needed = weight to lose (kg) × 7,700 kcal
Daily deficit = total deficit ÷ (weeks × 7)
Target intake = TDEE − daily deficit
Worked example: a 32-year-old man, 90 kg, 178 cm, moderate activity. BMR = 10×90 + 6.25×178 − 5×32 + 5 = 900 + 1,112.5 − 160 + 5 = 1,857.5 kcal. TDEE = 1,857.5 × 1.55 = 2,879 kcal/day. Goal: 75 kg over 20 weeks → 15 kg × 7,700 = 115,500 kcal total ÷ 140 days = 825 kcal/day deficit. Target intake = 2,879 − 825 = 2,054 kcal/day. Projected weekly loss = 825 × 7 ÷ 7,700 ≈ 0.75 kg/week — a healthy, sustainable rate.
Take a 28-year-old woman, 80 kg, 165 cm, lightly active, who wants to lose 20 kg in 8 weeks. BMR = 10×80 + 6.25×165 − 5×28 − 161 = 800 + 1,031.25 − 140 − 161 = 1,530 kcal. TDEE ≈ 1,530 × 1.375 = 2,104 kcal/day. But 20 kg in 56 days demands a 2,750 kcal/day deficit — a target intake of negative 646 kcal/day. The calculator will show this is impossible and below the safety floor. The lesson: extend the timeline. Over 24 weeks the daily deficit becomes a manageable ~917 kcal/day with a target of ~1,187 kcal/day — still aggressive, which is exactly the kind of call a professional should weigh in on.
Calorie Calculator — the companion tool for dialing in daily calorie targets.
BMR Calculator — compute your basal metabolic rate in isolation.
TDEE Calculator — total daily energy expenditure for any activity level.
Body Fat Calculator — track fat loss vs. muscle loss as the scale moves.
One Rep Max Calculator — preserve strength and muscle with resistance-training benchmarks while cutting.
This page is a free weight loss calculator on Sigma Calculator (sigmacalculator.net) that builds a daily calorie plan from a weight goal: inputs are current/goal weight (kg/lbs), timeline (weeks), age, height, sex, and activity level; it computes BMR via Mifflin-St Jeor, TDEE, required daily deficit (1 lb ≈ 3,500 kcal / 1 kg ≈ 7,700 kcal), target daily intake, and projected weekly loss, with a safety-floor warning below 1,200 kcal/day (women) or 1,500 kcal/day (men). Informational only — consult a health professional for aggressive targets.
Roughly 1 kg of fat ≈ 7,700 kcal, so losing 1 kg/week requires about a 1,100 kcal/day deficit from your TDEE. Whether that is safe depends on your TDEE — for smaller people it can push intake below the 1,200/1,500 kcal safety floors, in which case a slower rate (0.5 kg/week) is wiser.
It is a useful starting framework, not a precise law. Metabolic adaptation, water retention, and muscle changes mean real-world loss rarely tracks the rule perfectly over long timelines. Use it to set a plan, then adjust your intake based on actual weekly weigh-ins.
Common guidance sets the floor at 1,200 kcal/day for women and 1,500 kcal/day for men without medical supervision. Below these levels it is hard to meet nutrient needs, and the risk of muscle loss and health complications rises — always involve a professional for aggressive targets.
As you lose weight, your BMR and TDEE shrink (a smaller body burns less), and metabolic adaptation can lower expenditure further. A deficit that worked at 90 kg may be near maintenance at 80 kg. Recalculate your TDEE at your new weight and adjust the plan.
Both help, but strength training is especially valuable: it preserves muscle mass, which keeps your BMR higher as you lose fat. Aim for resistance training 2–4 times per week alongside whatever cardio you enjoy.
Cite this page as: “Weight Loss Calculator.” Sigma Calculator. Accessed October 20, 2026. https://sigmacalculator.net/fitness-health-calculators/weight-loss-calculator/
Last updated: October 20, 2026